Reverse current relay and system



w. R. HOLMES I 2,455,060

REVERSE CURRENT RELAY AND SYSTEM Filed July 26, 1946 INVENTOR WILL/HM H. H MES BY I n ATTORN EY Nov. 30. 1948.

Patented Nov. so, 1948 REVERSE CURRENT RELAY SYSTEM William R. Holmes, New York, N. Y., assignor to Bendix Aviation Corporation, Teterboro, N. 1., a corporation of Delaware Application July 26. 1946, sci-m No. 686,4 '1 Claims. (01. 320-33) 1 The present invention relates to electrical control systems and devices and more particularly to a novel reverse current relay or switch mechanism for a generator.

An object of the invention is to provide a novelerator and battery circuits as described above,

which means will withstand severe vibration immediately prior to and after the predetermined points 01' operation.

Another object of the invention is to provide a novel means to connect and disconnect the generator and battery circuits as described, which means will withstand severe conditions of acceleration and deceleration without failure or misoperation.

Another object of the invention is to provide a novel means to connect and disconnect the generator and battery circuits as previously described, which means will disconnect the generator from the battery on reverse current flow from the battery to the generator whether the reverse current is small in value or a heavy surge as may occur on opening the generator ileld' switch or as result of a dead short on the generator terminals.

Another object of the invention is to provide a novel means to connect and disconnect the generator and battery circuits as previously described, which means will operate at predetermined values regardless of the attitude or position of the said means with respect to the force of gravity.

Another object of the invention is to provide a novel means to connect and disconnect the generator and battery circuits as herein described, which means will operate at predetermined values within a small range of deviation when used continuously over long periods of time.

Another object of the invention is to build such a means without the use of permanent magnets or small delicate contact making devices or shock mounts.

These and other objects and features of the invention are pointed out in the following description in terms of the embodiment thereof which is shown in the accompanying drawings. It

is to be understood, however, that the drawing is for the purpose of illustration only, and is not designed as a definitionvof the limits of the invention, reference being had to the appended claims for this purpose.

Thedrawing is a circuit diagram illustrating a control system for a generator and the operation of the novel reverse current relay.

Referring to the drawing, there is shown a gen erator l of conventional type having a positively charged output line 2 and a negatively charged output line 3. Connected across the output lines 2 and 3 is a shunt field winding 4.

A variable resistance carbon pile element 5 controls the energization of the field winding 4 which in turn controls the output of the generator i in a manner well known in the art.

The carbon pile element 5 forms one element of a carbon pile regulator shown diagrammatically in the drawing as including an armature 6 pivoted at I and exerting a compressive force upon the carbon pile element 5 under tension of a spring 8. The position of the armature 6 is controlled by an electromagnetic winding 9 having a core and extertin-g an electromagnetic force acting in opposition to the spring 8. The winding 9 is connected across the output lines 2 and 3 oi the generator I. The spring 8 is arranged so as to balance the pull on the armature 6 by the electromagnet 9 when the electromagnet 9 is energized by a generator voltage having a predetermined value.

The regulator is preferably of a type such as shown in the copending patent application Ser. No. 612,691, filed August 25, 1945, by William G. Neild.

A line switch in normally biased under tension of a spring ll into an open position controls the contacts IOA and [0B and thereby the connection of the lines 2 and 8 to a battery l2 and a suitable load [3. The line switch I i is biased to a position closing contacts IDA and 1013 upon energization of an electromagnetic winding H. The contact I 0A is connected to the conductor 2 while the contact lllB is connected as will be explained hereinafter through a suitable conductor to the battery l2 and load l3.

The energization of the electromagnetic winding H is controlled by a novel switch mechanism or pilot relay indicated generally by the numeral I5 and which forms the subject matter of the present application.

The relay mechanism i5 includes an E-shaped magnet core I6 formed of a suitable ferro magnetic material having legs ll, l8, and I9. An

armature 20 is pivotally mounted at 2| above the center of the middle leg I8. A spring member 22 secured at one end to the E-shaped core I6 and at the other end to the armature 20 normally biases the armature 23 in a clockwise direction about the pivot 2| into the position shown in the drawing.

The armature 20 has mounted thereon and electrically connected to the armature 20 two leaf spring contactors 33 and 23. The contactor 23 cooperates with a switch contact 25, while the contactor 24 cooperates with a switch contact 26. The contactor 23 is arranged to close the contact 25 before the contactor 24 closes the contact 26 upon movement of the armature 26 in a counterclockwise direction in opposition to the biasing force of the spring 22.

On the leg I1 of the E-shaped core 65 there is wound an electromagnetic winding or voltage coil 21 connected through conductors 28 and 29 across the generator output lines 2 and 3. The winding 21 at a predetermined generator output voltage moves the armature 28 in a counterclockwise direction causing contactor 23 to'close contact 25.

A conductor 30 leads from line 2 to armature 20 which is electrically connected to contactor 23, while contact 25 is connected by conductor 3| to'one end of a second electromagnetic winding or differential current coil 32 on the leg 61.- The opposite end of the winding 32 is connected by a conductor 33 to a conductor 34 which leads from the line switch contact MB to the positive side of the battery l2 and load i3. Thus upon switch contactor 23 closing contact 25 the winding 32 is connected across switch contacts WA and IUB and in series with the generator 8 and battery I2.

Upon the generator voltage being sufflciently greater than the battery voltage the series or current winding 32 will exert an additive effect on the magnetic force of the winding 21 tending to move the armature 20 against the biasing force of the leaf spring contactor 23, which now engages contact 25, and the biasing force of spring 22 so as to cause switch contactor 24 to close contact 26.

When the voltage of the battery I2 exceeds that of the generator I, there is a. currentflow in the opposite direction and from the battery I2 causing the series or current winding 32 to eifect a magnet force of opposite polarity to that of the winding 21 and which opposes the magnetic force of the winding 21 so as to tend to nullify the pull of the voltage winding 21 on the armature 28.

However, upon the voltage of the generator I exceeding that of the battery I2 by a predetermined value, the armature 28 is drawn in a counterclockwise direction, so as to cause the leaf spring contactor 24 to close contact 26.

The contactor 24 is connected through armature 28 and conductor 38 to line 2, while the contact 26 is connected through a conductor 35 to one end of the electromagnetic winding I4 of the line switch relay Ill. The other end of the electromagnetic winding I4 is connected by a conductor 36 to the line 3.

Thus upon the closing of contact 26 by the contactor 24=the electromagnetic winding I4 is energized causing the line switch I to close contacts IDA and IOB and connecting line 2 g of the battery I2 and load I3.

4 leg I8 of the E shaped core I5 are windings or current coils 31 and 38, respectively.

The windings 31 and 38 are connected in series in the main supply line 34 leading from line switch contact IUB to the positive terminal The windings 31 and 38 are wound of relatively large sized wire and winding 38 has a, relatively smaller number of turns than the winding 31.

Upon the-line switch I8 closing contacts IDA and IIIB the windings 31 and 38 are energized. The winding 31 on the middle leg I9 aids the pull of the voltage coil 21 when current flows from the generator, I to the battery I2 and load I3, but the current winding 31 tends to nullify this pull when the current flows in a reverse direction from the battery I2 to the generator I.

The current winding 38 on the third leg I9 aids the effect of the winding 31 on the middle leg I8 and tends to bias the armature 28 in a clockwise direction or to its spring restrained position. The pull of this winding 38 does not exist unless the line switch Ill is closed and under normal line current conditions its pull is small. However, under large current surges the pull of the winding 38 is great.

In the latter event, the magnetic flux gener ated by the winding 38 will aid the spring 22 in rotating the armature 20 in a clockwise direction so as to open contacts 24 and 26 when the flux generated by the winding 31 tends to bal-.

ance that of the winding 21. It is this additional force provided by the winding 38 which assures opening of the contacts 24 and 26 before the flux generated by the coil 31 has had a chance to build up sufliciently ina reverse direction to exceed the flux of the coil 21 or freeze the contacts 24 and 26 closed.

In the operation of the reverse current relay 40 I5 thus described, it will be seen that upon initiating operation of the generator I a voltage will build up as the generator gains in speed and excitation. When this voltage is still below the predetermined operating value, which may be slightly above the voltage of the battery I2, the armature 20 remains spring retained and contacts 25 and 26 remain open. If the relay mechanism I5 is subjected to severe vibration under these conditions, the armature 28 may tend to move in a counterclockwise direction under such vibrational forces, but the same will be restrained by the spring force of the contactor 23 on closing contact 25 so that not sufllcient movement is effected to close contact 26.

Therefore the electromagnetic winding .I4 may does not produce added pull to the voltage coil 21 by virtue of the closing of the circuit to the differential coil 32 because the voltage of the generator I is still equal to or lower than the voltage of the battery I2.

When, the voltage of the generator I increases in value slightly above the voltage of the battery I2 and reaches the predetermined operating value, the pull of the voltage coil 21 will cause contactor 23 to close contact 25. The closing of contact 25 will effect the energization of the differential coil 32 producing an additional pull on the armature 20, whereupon the armature 20 moves to cause contactor 24 to close contact 26 and to reach its final position.

- operated by the electromagnetic force of winding II.

The closing of contacts WA and IOB by the switch ID causes current to flow to the battery I2 from the generator i and to any connected load through the series coils 31 and 38.

The line current, if flowing from the generator 1, causes the series coil 31 on the middle leg I8 to aid the pull of the voltage coil 21. The pull of the series coil 38 on the third leg is produces very little restraining pull as there are relatively few turns in the coil 38.

The addition of the magnetic force of the voltage coil 21 and the current coil 37 on the center leg It holds the armature down with contacts 24 and 26 closed and with these contacts having sufficient overtravel the same will withstand severe vibrational forces. It will be noted that the differential coil 32 will be shorted out upon the closing of contacts 16A and ME by the switch iii and therefore the coil 32 is energized only during the closing period.

Should the voltage of the generator i drop below that of the battery i 2, a reverse how of current through the coil 37 will nullify in whole or in part the electromagnetic force of the voltage coil 21 and cause the armature 20 to be returned under the biasing force of the spring 22 to the original or open position. Should this reverse current become large, the pull of the coil 38 on the third leg i9 will be strong enough to bias the armature 2!) so as to open the contacts 24 and 26 and return the armature iii to its original open position.

Heretofore in the conventional type of reverse current relay, a heavy surge of current in the reverse direction would not allow the to open the main line circuit, because the magnetic flux generated by the current winding would overcome that generated by the voltage winding and exert suflicient additional force to hold the relay closed. In my present invention, however, the winding 38 adds to the effect of wind= ing 37 in such a manner as to assure the opening of the relay contacts 2 2 and 26 upon such a reverse current surge.

In the latter operation, the magnetic flux generated by the winding 38 will be available to aid the spring 22 in rotating the armature inc. clockwise direction to thereby open the contacts 24 and 26 when the flux generated by the winding 3? has substantially or completely neutralized that of the winding 21. It is the extra forceprovided by the winding 38 that assures opening of the contacts 24 and it before the flux generated by the coil 31 has had a chance to build upsufliciently in a reverse direction to overcome the flux of the coil 2! and which might otherwise freeze the contacts 24 and 25 closed.

Although only one embodiment of the invention has been illustrated and described, various changes in the form and relative arrangements of the parts, which will now appear to those skilled in the art, may be made without departing from the scope of the invention. Reference is, therefore, to be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

l. A relay mechanism to control connection and disconnection of a generator to a battery charging circuit, comprising, in combination, an E-shaped magnet core, a pair of coils wound on an outer leg of the E-shaped core, one of said coils responsive to the output voltage of the generator and the other of said coils responsive to the current flow between the generator and battery circuit, other 'current coils wound on the center leg and other outer leg of the E-shaped core and responsive to the flow of current between the generator and battery circuit, and an armature cooperating with the legs of said E-shaped core and including switch elements for connecting said current coils in and out of operation.

2. A relay mechanism to control connection and disconnection of a generator. to a battery charging circuit, comprising, in combination, an E-shaped magnet core, a pair of coils wound on an outer leg of the E-shaped core; one ofsaid coils responsive to the output voltage of the generator and the other of said coils responsive to the current flow between the generator and battery circuit, other current coils wound on'the center leg and other outer leg of the E-shaped core and responsive to the flow of current between the generator and battery circuit, an armature pivotally mounted above the middle leg of the iii-shaped core, the voltage coil being arranged so as to bias the armature toward the first mentioned outer leg, switch means carried by said armature for connecting said current coils in and out of operation, the current coil wound on the center leg. being arranged so as to counteract the magnetic force of the voltage coil under conditions of reverse current flow from the battery to the generator, and the current coil wound on the other outer leg being arranged so as to assist the iorces of the center leg current coil and to oppose the forces applied to the armature by the voltage coil so as to bias the armature away from the first mentioned outer leg and toward said other outer leg of the E-shaped core.

3. A relay mechanism to control connection and disconnection of a generator to a battery circuit, comprising, in combination, an E-shaped magnet core, an armature extending across the legs of said core and pivoted above the center leg of said core, a coil wound on one of the outer legs of said core and responsive to the output voltage of the generator, 2. second coil Wound on said one outer leg, a third coil wound on the center leg, a forth coil wound on the other outer leg of said core, said third and fourth coils being connected in series, a first switch means operated by said armature, a second switch means operated by said armature, said first switch means closing a circuit between the generator and battery for energizing said second coil upon movement of the armature toward said one outer leg, and said second switch means effecting the closing of a circuit between said generator and battery for energizing said third and fourth coils upon further movement of said armature toward said one outer leg.

4i. A relay mechanism .to control connection and disconnection of a generator to a battery circuit, comprising, in combination, an E-shaped magnet core, an armature extending across the legs of said core and pivoted above the center leg of said core, a coil wound on one of the outer legs of said core and responsive to the output voltage of the generator, a second coil wound on said one outer leg, a third coil wound on the center leg, a fourth coil Wound on the other outer leg of said core, said third and fourth coils being connected in series, a first switch means operated by said armature, a second switch means operated by said armature, said first switch means closing a circuit between the generator and battery for energizing said second coil upon movement of the armature toward said one outer leg, and said second switch means effecting the closing of a circuit between said generator and battery for energizing said third and fourth coils upon further movement 01' said armature toward said one outer leg, and spring means for biasing said armature in a direction towards said other outer leg f or opening said circuits.

5. A relay mechanism to control connection and disconnection of a generator to a battery circuit, comprising, in combination, an E-shaped magnet core, an armature extending across the legs iii of said core and pivoted above the center leg oi 1 said core, a coil wound on one of the outer legs of said core and responsive to the output voltage of the generator, a second coil wound on said one outer leg, a third coil wound on the center leg, a fourth coil wound on the other outer le of said core, said third and fourth coils being connected in series, a first switch means operated by said armature, a second switch means operated by said armature, said first switch means closing a circuit between the generator and battery for energizing said second coil upon movement of the armature toward said one outer leg, and said second switch means effecting the closing of a circuit between said generator and battery for energizing said third and fourth coils upon further movement of said armature toward said one outer leg, and said fourth coil for biasing said armature in a direction towards said other outer leg upon heavy current surges from said battery.

6. A relay mechanism to control connection and disconnection oi a generator to a battery circuit, comprising, in combination, an E-shaped magnet core, an armature extending across the legs of said core and pivoted above the center leg of said core, a coil wound on one of the outer legs of said core and responsive to the output voltage of the generator, a second coil wound on said one outer leg, a third coil Wound on the center leg, a fourth coil wound on the other outer leg of said core, said third and fourth cells being connected in series, a first switch means operated by said or mature, a second switch means operated by said armature, said first switch means closing a ctr cuit between the generator and battery ior en ergizing said second coil upon movement or the armature toward said one outer leg, and said second switch means effecting the closing of a circuit between said generator and battery for energizing said third and fourth coils upon further movement of said armature toward said one outer leg, spring means for biasing said armature in a direction towards said other outer leg for opening said circuits, and said fourth coil for biasing said armature in a direction towards said other outer leg upon heavy current surges from said battery.

l. A. relay mechanism to control connection an disconnection of a generator toa battery circuit, comprising, in combination, on ii=shaped i'nasnet core, on armature extending across the legs of said core and pivoted above the center leg of said core, a coil wound on one of the outer legs of said core and responsive to the output voltage oi the generator, a second coll wound on said one outer leg, a third coil wound on the center leg. a fourth coil wound on the other outer leg oi! said core, said third and fourth coils being connected in series, a first switch means operated by said armature, a second switch means operated by said armature, said first switch means closing a circuit between the generator and battery for energizing said second coil upon movement of the armature toward said one outer leg, and said second switch means effecting the closing of a circuit between said generator and battery for energizing said third and fourth coils upon further movement of said armature toward said one l/iiLL'iAM R. HOM S.

accessories @Z'Eidii The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Home Date 1,7523% Eisenmann Apr. 1, 1930 1,386,629 Blake Nov, 8, 1932 2,285,937 Mishelevich June 9, 1942 

